In opthalmic surgery, following removal of the lens of the eye, an intraocular lens is implanted to take the place of the lens removed. Various type of such lenses have been proposed and are in use. Lenses designed to be placed in the posterior chamber may be implanted in either the ciliary sulcus or the capsular bag of the eye. For example, U.S. Pat. No. 4,159,546 discloses an intraocular lens supported by a plurality of flexible strands secured to the lens body. The strands permit the lens to be supported in the posterior chamber of the eye. Numerous other lens designs are shown in the The Intraocular Implant Lens Development and Results, published by the Williams and Wilkens Company, Baltimore, Md., 1975, pages 16-23.
Although great advances have been made over the years in intraocular lenses, the prior art designs are not without their problems. The very common "J-looped" lenses (see FIG. 1B) are made in varying sizes depending upon whether they are meant to be placed in the capsular bag or the ciliary sulcus. The J-loops are not very compressible, and therefore if a large lens is placed within the capsular bag, it is a difficult fit. On the other hand, a small lens which is meant to go into the capsular bag may "rattle about" and irritate intraocular structures and get out of position if placed in the ciliary sulcus. It is often particularly difficult for the surgeon to be sure that a lens which is meant to be placed in the capsular bag is indeed in the bag, or that one which is placed in the sulcus is indeed solely in the sulcus and not in the bag. Sometimes, one loop is placed in the bag and the second loop in the sulcus in spite of the surgeon's best efforts.
Another problem with "J-looped" lenses is their poor compressibility, which makes them difficult to insert, since once in place in the anterior chamber, they must be rotated, or "dialed" into proper position in the posterior chamber. This requires the surgeon to make two separate movements to properly place the lens.
Other prior art lenses (see FIG. 1A) have very long gently curving loops which exert gentle pressure and are easily compressible, but, because of the extreme length of the loop, the lens is much more difficult to implant. This type of lens requires intraocular manipulation to place it into position in the posterior chamber behind the iris after the lens has been placed preliminarily in the anterior chamber. Thereafter, the lens must be pushed into the eye from anterior to posterior chamber. This increased intraocular manipulation increases the risk of injury to the eye.
The present invention avoids these problems by allowing each lens support strand to be compressed radially for a considerable distance without significantly increasing the reaction force exerted outward toward the lens optic. An advantage of this design is that the lens will push outward with about the same force regardless of whether the loop is compressed mildly if it lies in the ciliary sulcus or compressed more strongly if it lies within the capsular bag.
The lens support strands of the present invention have flat or straight ends. This offers the advantage of allowing the surgeon to more readily place the lens without the need for rotating or "dialing" the lens into place.
Another advantage of this design is that the diameter of the lens becomes less critical. It is no longer necessary to use a large lens for the ciliary sulcus or a small lens for the capsular bag.
A further advantage of the present invention is that the gentle force directed radially outwardly by the loops, and the compressibility of the loops, allow the lens to be placed equally advantageously whether both strands are located in the capsular bag, in the sulcus, or one strand in each. The gentle compression is less likely to tear the zonal suspensionary ligament of the human lens.
Furthermore, the compressibility of the strands of the present invention require less intraocular manipulation to locate the lens properly within the eye. The lens of the present invention simply can be grasped by implantation forceps and be placed in one straight movement behind the iris into the ciliary sulcus or capsular bag. Thus, rotation of the lens, or "dialing", is unnecessary with the present invention. It is also easy to compress the loops in the forceps when inserting the lens, further simplifying straight-line insertion. The surgeon simply inserts the lens, places it in position and lets go.